Ronnie O'Sullivan was impressive winning the Masters in January but 9-4 (general) looks too short a price. Photograph: ChinaFotoPress/Getty Images

With Ronnie O'Sullivan continuing to baffle and beguile punters it is fitting that the world snooker championship's new sponsor is the bookmaker Betfred.com. Over the years, the enigmatic world No1 has profited layers and frustrated bettors. And despite the usual question marks surrounding his game and attitude, the Rocket is again the market leader, at 9-4 (general), by some distance going into this year's tournament, which begins at the Crucible tomorrow.

O'Sullivan claimed a third world title 12 months ago when he was available ante-post at 7–2. A year on, it is hard to see how his form can justify a much shorter quote. Last season he had won the UK Champ­ionship and the Premier League, this term he can boast success in the Northern Ireland Trophy, the Masters and the Premier League. In terms of ranking points, the 2007-08 campaign earned O'Sullivan more going into the world championship.

Admittedly, his win at the Masters in January was nothing short of incredible. A self-smashed cue in the run-up to the event meant O'Sullivan had to use a new one at Wembley (some players use the same one for practically an entire career) and he has since switched again. It is questionable, though, just how long he can go on defying conventional wisdom and although there have been some lumpy bets on him, such as a £3,000 bet at 2–1 stood by extrabet.com, at current odds he is poor value.

Stephen Maguire is the joint second favourite, with 8–1 freely available. The No2 seed meets Jamie Burnett in the first round, a draw that embarrassed snooker officials as the pair's UK Championship meeting was still under investigation by the gambling commission following match-fixing suspicions.

Maguire peaked too soon last year, looking in imperious form in the early rounds before going out to Joe Perry in the quarter-final, while in 2007 he should have defeated the eventual winner John Higgins in the semi-final. So there are, perhaps, question marks about whether Maguire has the ability to produce his best snooker at the right time.

Mark Selby, also at 8–1 (general), looks a better bet but, as the Leicester man is in the same half of the draw as O'Sullivan, back him instead at 15–8 (Paddy Power and Sky Bet) to win his quarter. Selby is not in the same sort of form as last year, when he entered the world championship off the back of wins in the Masters and the Welsh Open, but there looked little wrong with his game when he finished runner-up to O'Sullivan in the Premier League final.

Those seeking an each-way interest should look to the bottom half of the draw, where Ali Carter (12–1, Betfred and extrabet.com) and Shaun Murphy (14–1, general) lurk. Carter, who finally broke his duck at a ranking tournament in the Welsh Open this year, has some heavy support (Paddy Power reports a £1,700 bet at 12–1) and has made the highest break in the past two years at the Crucible (he is 14–1, generally, to do so again). But the preference is for the 2005 champion Murphy, who won this season's UK Championship. Back him with Sky Bet which, along with Boylesports, offers each-way terms of a fifth of the odds for the first four players.

Intriguingly, extrabet.com has reported buyers of total tournament centuries at 69 (the biggest at £500 per century). The highest number of century breaks made in the past has been 68 (twice) but with the tables set to be reclothed twice this year (instead of once) punters are predicting truer surfaces for longer and therefore a higher number of big scores.

This, of course, will help all players and extrabet.com may well have under­estimated Jamie Cope's break-building capability, quoting a spread of 116–118 about the Stoke professional's highest tournament score. In this season's Shanghai Masters Cope recorded a 147 while he can also boast a break of 155, the highest possible in the game, in a practice match.